Disable scheduled CI runs on forks (#14366)

The three scheduled CI runs are running on forks of the main repo, e.g.
https://github.com/ianthomas23/ipython/actions. They can be disabled by
each fork owner, but this PR disables them for all forks.

.github/workflows/downstream.yml

@@ -14,6 +14,8 b' permissions:'
 jobs:
   test:
     runs-on: ${{ matrix.os }}
+    # Disable scheduled CI runs on forks
+    if: github.event_name != 'schedule' || github.repository_owner == 'ipython'
     strategy:
       matrix:
         os: [ubuntu-latest]

.github/workflows/nightly-wheel-build.yml

@@ -9,8 +9,8 b' jobs:'
   upload_anaconda:
     name: Upload to Anaconda
     runs-on: ubuntu-latest
-    # The artifacts cannot be uploaded on PRs
-    if: github.event_name != 'pull_request'
+    # The artifacts cannot be uploaded on PRs, also disable scheduled CI runs on forks
+    if: github.event_name != 'pull_request' && (github.event_name != 'schedule' || github.repository_owner == 'ipython')
 
     steps:
       - uses: actions/checkout@v3

.github/workflows/test.yml

@@ -15,6 +15,8 b' on:'
 jobs:
   test:
     runs-on: ${{ matrix.os }}
+    # Disable scheduled CI runs on forks
+    if: github.event_name != 'schedule' || github.repository_owner == 'ipython'
     strategy:
       fail-fast: false
       matrix: